• 제어로봇시스템학회논문지
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• 제14권8호
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• pp.727-732
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• 2008

In this paper, the state-space representation of generalized complimentary filter is proposed. Complementary filter has the suitable structure to merge information from sensors whose frequency regions are complementary. First, the basic concept and structure of complementary filter is introduced. And then the structure of the generalized filter and its state-space representation are proposed. The state-space representation of complementary filter is able to design the complementary filter by applying modern filtering techniques like Kalman filter and $H_{\infty}$ filter. To show the usability of the proposed state-space representation, the design of Inertial Navigation System(INS) vertical channel damping loop using Global Positioning System(GPS) is described. The proposed GPS/INS damping loop lends the structure of Baro/INS(Barometer/INS) vertical channel damping loop that is an application of complementary filter. GPS altitude error has the non-stationary statistics although GPS offers navigation information which is insensitive to time and place. Therefore, $H_{\infty}$ filtering technique is selected for adding robustness to the loop. First, the state-space representation of GPS/INS damping loop is acquired. And next the weighted $H_{\infty}$ norm proposed in order to suitably consider characteristics of sensor errors is used for getting filter gains. Simulation results show that the proposed filter provides better performance than the conventional vertical channel loop design schemes even when error statistics are unknown.

• 천문학회보
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• 제46권2호
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• pp.78.3-79
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• 2021

Coronal Diagnostic Experiment (CODEX) is a diagnostic coronagraph developed by the Korea Astronomy and Space Science Institute and the NASA Goddard Space Flight Center (GSFC) to be deployed in 2023 on the International Space Station (ISS). It is designed to obtain simultaneous measurements of electron density, temperature, and velocity in the 2.5 - 10 solar radius range using multiple filters. The filters are mounted in two filter wheel assemblies (FWAs), which have five filter positions each. One position of each FWA is occupied by windows, and remaining eight positions are occupied by three bandpass filters for temperature, two bandpass filters for velocity, one Ca II H filter for F-corona, one broadband filter for fast imaging and density, and one neutral density (ND) filter for direct Sun viewing and safety.

• 천문학회보
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• 제46권1호
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• pp.37.3-38
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• 2021

Radiation pressure noise of photon and photon shot noise are quantum noise limitation in interferometric gravita-tional wave detectors. Since relationship between the two noises is position and momentum of the Heisenberg uncertainty principle, quantum non-demolition (QND) technique is required to reduce the two noises at the same time. Frequency dependent squeezing using a filter cavity is one of realistic solutions for QND measurement and experimental results show that its cutting-edge performance is sufficient to apply to the current gravitational wave detectors. A 300m filter cavity is under construction at adv-LIGO. KAGRA (gravitational wave detector in Japan) has also started international collaboration to build a filter cavity. Recently we joined the filter cavity project for KAGRA. Current status of squeezing and filter cavity research at KASI and details of the KAGRA filter cavity project will be presented.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2002년도 ICCAS
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• pp.45.2-45
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• 2002

$\textbullet$ Uncertainties are described by sum quadratic constraint(SQC) $\textbullet$ SQC is converted into an indefinite quadratic cost function $\textbullet$ A Kalman filter developed in indefinite inner product space is Krein space Kalman filter $\textbullet$ To minimize the SQC, the Krein space Kalman filter is used $\textbullet$ The proposed robust filter outperforms the standard Kalman filter and existing robust Kalman filter $\textbullet$ The proposed filter has the same recursive, simple structure as the standard Kalman filter $\textbullet$ Easy to design, adequate for on-line implementation

• Journal of Astronomy and Space Sciences
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• 제22권4호
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• pp.501-512
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• 2005

본 논문에서는 우주개발 중장기계획에 따라 개발 중인 KSLV-I 우주발사체가 나로 우주센터에서 발사될 경우를 가정하여 확장칼만필터와 Unscented 칼만필터를 통한 실시간 궤적추정 결과를 비교 분석하였다. 이를 위해 가상의 KSLV-I과 관측 레이더 3기를 바탕으로 실제 궤적을 생성하였으며, 관측자료는 실제 궤적에 관측오차를 고려하여 생성하였다. 이에 대해 초기 추정오차가 작은 경우와 큰 경우로 구분하고, 관측주기가 20Hz와 10Hz인 경우로 나누어 각각 두 필터를 적용해서 성능을 비교하였다. Unscented 칼만필터는 확장칼만필터보다 큰 초기 추정오차에 대해 수렴이 빠르고 정확도가 높으며, 느린 관측주기에도 우수한 성능을 보이는 것을 확인하였다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2004년도 ICCAS
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• pp.223-226
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• 2004

This paper analyzes the accuracy of free space path loss and matched filter gain approximated by using a passband rectangular pulse for ultra wideband (UWB) radio systems. The example causal signal, a modulated Gaussian pulse with the same center frequency and frequency bandwidth of the passband rectangular pulse, is used to consider the accuracy. The path loss and matched filter gain of the modulated Gaussian pulse are simulated for the reference results. The UWB free space path loss is shown and is compared with that obtained from simulation and Friis' transmission formula. The UWB matched filter gain is shown and compared with simulation results. From the results, we can see that the UWB path loss formula is more accurate than the Friis' transmission formula. The results from the UWB free space path loss and matched filter gain formulas agree with the simulation. Then, these free space path loss and matched filter gain formulas approximated by using a passband rectangular pulse are appropriate for UWB system.

• 한국항행학회논문지
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• 제25권6호
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• pp.543-549
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• 2021

본 논문에서는 불확실성의 크기가 유한한 파라미터를 갖는 스트랩다운 관성항법시스템에 대한 강인한 전달정렬 기법을 제안하였다. 크레인 공간을 이용하면 에너지가 유한한 불확실성을 갖는 강인한 필터는 일반적인 칼만필터와 동일한 구조를 갖게 된다. 단지 측정 행렬과 측정 잡음의 공분산값을 수정하면 된다. 본 논문에서 제안한 강인한 전달정렬 기법의 성능을 분석하기 위해서 항체가 고기동 운항을 하면서 측정치에 시간 지연이 발생하는 경우를 가정하여 시뮬레이션을 수행하였고 제안한 기법의 강인성을 검증하였다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2005년도 ICCAS
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• pp.894-900
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• 2005

A new approach to the straightforward implementation of the unscented filter in a unit quaternion space is proposed for spacecraft attitude estimation. Since the unscented filter is formulated in a vector space and the unit quaternions do not belong to a vector space but lie on a nonlinear manifold, the weighted sum of quaternion samples does not produce a unit quaternion estimate. To overcome this difficulty, a method of weighted mean computation for quaternions is derived in rotational space, leading to a quaternion with unit norm. A quaternion multiplication is used for predicted covariance computation and quaternion update, which makes a quaternion in a filter lie in the unit quaternion space. Since the quaternion process noise increases the uncertainty in attitude orientation, modeling it either as the vector part of a quaternion or as a rotation vector is considered. Simulation results illustrate that the proposed approach successfully estimates spacecraft attitude for large initial errors and high tip-off rates, and modeling the quaternion process noise as a rotation vector is more optimal than handling it as the vector part of a quaternion.

• 천문학회보
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• 제46권2호
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• pp.76.1-76.1
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• 2021

Maemi Dual Field Telescope System (MDFTS) is a dual telescope system located at Kyung Hee University. The system consists of 0.4 m telescope and 0.1 m telescope for wide-field observation. The 0.4 m telescope provides photometric observation which covers a field of view of 21'×16'. It has been used for various purposes with Johnson-Cousins UBVRI broadband filter system, e.g., SomangNet and Intensive Monitoring Survey of Nearby Galaxies. In this poster, we present the standard calibration result for our broadband filter system. Also, we suggest a new usage of the KHAO 0.4m telescope which is narrowband photometry by demonstrating the standard calibration of H-alpha filter. For flux calibration, not only R filter but also V filter is used for compensating the central wavelength discrepancy between R filter and H-alpha filter.

• Journal of Astronomy and Space Sciences
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• 제25권3호
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• pp.283-290
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• 2008

이 논문에서는 간섭계 구성의 기본이 되는 위성 간 상대위치 추정에 관한 알고리즘을 개발하고 검증하였다. 편대위성 간 상대위치 추정을 실시간으로 수행하기 위해 확장칼만필터 (EKF, Extended Kalman Filter)와 Unscented 칼만필터 (UKF, Unscented Kalman Filter) 를 사용하였다. 칼만 필터를 이용한 상태벡터 (state-vector)의 갱신(update)을 위한 관측 데이터는 시뮬레이션을 통해 얻어진 GPS 위성 신호의 단일차분 (Single Difference)에 대한 값을 사용하였다. 이 연구에서 개발한 알고리즘으로 추정된 편대위성 간 상대위치는 확장칼만필터와 Unscented 칼만필터 모두 참 값으로 가정한 STK(Satellite Tool Kit) 의 시뮬레이션된 관측 값에 대해 ${\pm}1m$ 이내의 오차로 수렴함을 확인하였다. 또한 두 종류의 칼만필터를 이용하여 상대위치 결정을 수행함으로써 비선 형성을 가지는 경우 Unscented 칼만필터의 성능이 상대적으로 우수함을 확인할 수 있었다.